timekeeping: Move TAI managment into timekeeping core from ntp

Currently NTP manages the TAI offset. Since there's plans for a
CLOCK_TAI clockid, push the TAI management into the timekeeping
core.

CC: Thomas Gleixner <tglx@linutronix.de>
CC: Eric Dumazet <eric.dumazet@gmail.com>
CC: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>

include/linux/time.h

@@ -181,6 +181,8 @@ extern struct timespec timespec_trunc(struct timespec t, unsigned gran);
 extern int timekeeping_valid_for_hres(void);
 extern u64 timekeeping_max_deferment(void);
 extern int timekeeping_inject_offset(struct timespec *ts);
+extern s32 timekeeping_get_tai_offset(void);
+extern void timekeeping_set_tai_offset(s32 tai_offset);
 
 struct tms;
 extern void do_sys_times(struct tms *);

include/linux/timekeeper_internal.h

@@ -62,6 +62,9 @@ struct timekeeper {
 	ktime_t			offs_boot;
 	/* The raw monotonic time for the CLOCK_MONOTONIC_RAW posix clock. */
 	struct timespec		raw_time;
+	/* The current UTC to TAI offset in seconds */
+	s32			tai_offset;
+
 	/* Seqlock for all timekeeper values */
 	seqlock_t		lock;
 };

kernel/time/ntp.c

@@ -53,9 +53,6 @@ static int			time_state = TIME_OK;
 /* clock status bits:							*/
 static int			time_status = STA_UNSYNC;
 
-/* TAI offset (secs):							*/
-static long			time_tai;
-
 /* time adjustment (nsecs):						*/
 static s64			time_offset;
 
@@ -415,7 +412,6 @@ int second_overflow(unsigned long secs)
 		else if (secs % 86400 == 0) {
 			leap = -1;
 			time_state = TIME_OOP;
-			time_tai++;
 			printk(KERN_NOTICE
 				"Clock: inserting leap second 23:59:60 UTC\n");
 		}
@@ -425,7 +421,6 @@ int second_overflow(unsigned long secs)
 			time_state = TIME_OK;
 		else if ((secs + 1) % 86400 == 0) {
 			leap = 1;
-			time_tai--;
 			time_state = TIME_WAIT;
 			printk(KERN_NOTICE
 				"Clock: deleting leap second 23:59:59 UTC\n");
@@ -579,7 +574,9 @@ static inline void process_adj_status(struct timex *txc, struct timespec *ts)
  * Called with ntp_lock held, so we can access and modify
  * all the global NTP state:
  */
-static inline void process_adjtimex_modes(struct timex *txc, struct timespec *ts)
+static inline void process_adjtimex_modes(struct timex *txc,
+						struct timespec *ts,
+						s32 *time_tai)
 {
 	if (txc->modes & ADJ_STATUS)
 		process_adj_status(txc, ts);
@@ -613,7 +610,7 @@ static inline void process_adjtimex_modes(struct timex *txc, struct timespec *ts
 	}
 
 	if (txc->modes & ADJ_TAI && txc->constant > 0)
-		time_tai = txc->constant;
+		*time_tai = txc->constant;
 
 	if (txc->modes & ADJ_OFFSET)
 		ntp_update_offset(txc->offset);
@@ -632,6 +629,7 @@ static inline void process_adjtimex_modes(struct timex *txc, struct timespec *ts
 int do_adjtimex(struct timex *txc)
 {
 	struct timespec ts;
+	u32 time_tai, orig_tai;
 	int result;
 
 	/* Validate the data before disabling interrupts */
@@ -671,6 +669,7 @@ int do_adjtimex(struct timex *txc)
 	}
 
 	getnstimeofday(&ts);
+	orig_tai = time_tai = timekeeping_get_tai_offset();
 
 	raw_spin_lock_irq(&ntp_lock);
 
@@ -687,7 +686,7 @@ int do_adjtimex(struct timex *txc)
 
 		/* If there are input parameters, then process them: */
 		if (txc->modes)
-			process_adjtimex_modes(txc, &ts);
+			process_adjtimex_modes(txc, &ts, &time_tai);
 
 		txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
 				  NTP_SCALE_SHIFT);
@@ -716,6 +715,9 @@ int do_adjtimex(struct timex *txc)
 
 	raw_spin_unlock_irq(&ntp_lock);
 
+	if (time_tai != orig_tai)
+		timekeeping_set_tai_offset(time_tai);
+
 	txc->time.tv_sec = ts.tv_sec;
 	txc->time.tv_usec = ts.tv_nsec;
 	if (!(time_status & STA_NANO))

kernel/time/timekeeping.c

@@ -513,6 +513,48 @@ error: /* even if we error out, we forwarded the time, so call update */
 }
 EXPORT_SYMBOL(timekeeping_inject_offset);
 
+
+/**
+ * timekeeping_get_tai_offset - Returns current TAI offset from UTC
+ *
+ */
+s32 timekeeping_get_tai_offset(void)
+{
+	struct timekeeper *tk = &timekeeper;
+	unsigned int seq;
+	s32 ret;
+
+	do {
+		seq = read_seqbegin(&tk->lock);
+		ret = tk->tai_offset;
+	} while (read_seqretry(&tk->lock, seq));
+
+	return ret;
+}
+
+/**
+ * __timekeeping_set_tai_offset - Lock free worker function
+ *
+ */
+void __timekeeping_set_tai_offset(struct timekeeper *tk, s32 tai_offset)
+{
+	tk->tai_offset = tai_offset;
+}
+
+/**
+ * timekeeping_set_tai_offset - Sets the current TAI offset from UTC
+ *
+ */
+void timekeeping_set_tai_offset(s32 tai_offset)
+{
+	struct timekeeper *tk = &timekeeper;
+	unsigned long flags;
+
+	write_seqlock_irqsave(&tk->lock, flags);
+	__timekeeping_set_tai_offset(tk, tai_offset);
+	write_sequnlock_irqrestore(&tk->lock, flags);
+}
+
 /**
  * change_clocksource - Swaps clocksources if a new one is available
  *
@@ -1143,6 +1185,8 @@ static inline void accumulate_nsecs_to_secs(struct timekeeper *tk)
 			tk_set_wall_to_mono(tk,
 				timespec_sub(tk->wall_to_monotonic, ts));
 
+			__timekeeping_set_tai_offset(tk, tk->tai_offset - leap);
+
 			clock_was_set_delayed();
 		}
 	}